The present invention pertains generally to the field or art of fabricating a housing which is transparent to light of selected wavelength. More specifically, the invention pertains to the fabrication of a housing for selected electro-optical equipment which requires the joining of a selectively shaped window of glass or other brittle material with a mounting of metallic material. Even more specifically, the invention pertains to the fabrication of a housing which includes a hyperhemispherical-shaped window and which may be employed to house a periscope or other device for a submarine.
The importance of a periscopic viewing device for the operation of submarines for military or other purposes is quite well known. Presently used periscopes generally comprise a system of lenses and mirrors enclosed in a tubular housing, which penetrates the hull of any submarine with which it is used in order to provide a path for received optical images. As is well known in the field of naval architecture, physical penetration weakens a submarine hull and reduces the resistance thereof to hydrostatic pressure.
In addition, certain presently used periscopes include a housing which is of circular cross-section so as to be rotatable about the longitudinal axis of the housing. Such rotation is necessary to enable view of a 360.degree. azimuth. However, a housing of circular cross section is not hydrodynamically streamlined, and increases wake and resistance to travel through water. Also, the wear on a mechanically rotatable housing may be substantial.
It has been recognized that the above disadvantages may be overcome by providing a periscope housing which includes a window of selected shape or configuration constructed from material which is transparent to light. The window could be joined to a mounting to enclose electro-optical viewing equipment, along with electromechanical equipment to maneuver the viewing equipment through a selected azimuth and angle of elevation. All movement required to view an object would thereby take place within the housing. Required power and control signals to the equipment and information therefrom could be coupled through electric cable, whereby very minimal penetration of a submarine hull would be required.
However, in fabricating a housing of the above type, it would most likely be necessary to sealably join a window of glass or similar brittle material with a mounting of metal, such as steel or titanium. Since the respective thermal coefficients of such joined materials are very different, their respective rates of flexure differ substantially as the joint therebetween is subjected to increasing pressure, leading to possible failure of the brittle material.